The context of the present invention is that of audiovisual servers capable of supplying audiovisual programmes on demand, and of any domestic device capable of displaying audiovisual programmes received from a terrestrial, microwave or satellite network and communicating with a server with the aid of a broadcast network. The audiovisual programme is typically transmitted over a one-way broadcast network. Access to the audiovisual programmes is usually conditional upon a payment by the user of the device. Electronic Program Guides (EPG for short) offer users a catalogue of audiovisual programmes, and particularly films. The user chooses a programme from this catalogue and after paying for the access rights, he receives the means of viewing it in clear. The programme is transmitted in encrypted form over the broadcast network and the receiver decrypts the programme by means of a previously received code. Another way of operating consists in setting up a call with the server supplying the programmes, interrogating its catalogue, and downloading the programme after a payment. The price, which is fixed by the programme supplier, is usually displayed by the EPG, so that the user knows the cost of the operation before committing himself.
Certain devices have a hard disk or some other means of storing programmes (cassette, cartridge, DVD-RAM, etc.). A programme can then be downloaded over the network directly to the hard disk, in compressed form, irrespective of the display constraints. The programme can then be downloaded at any moment, without the user's intervention, and at a time that does not disturb him, at night for example. The programme is stored as it is received. During viewing, the device reads the programme from the storage means, decompresses it and sends the audiovisual signals to a screen.
In fact the profitability of a download fluctuates considerably depending on the circumstances. One of the aims of the present invention is to be able to optimise the profitability of such downloads.